岩质边坡复合型破坏机制的改进运动单元法研究

Investigation on combined failure mechanism of rock slope based on the improved kinematical element method

目前运动单元法的研究主要集中于土质边坡,未涉及到岩质边坡稳定性分析问题;而岩体中孕育有不同特性的结构面,控制着岩质边坡的力学行为。为求解结构面控制作用下岩质边坡“结构面滑移-岩桥剪断”复合型破坏问题,研究了塑性滑移区节点在岩桥内和结构面上的运动约束条件,推导了含结构面的运动单元计算公式,提出了改进运动单元法。通过经典算例的对比分析,验证了改进运动单元法计算结果的准确性。研究结果表明:岩桥位置、结构面贯通度和结构面倾角是控制岩质边坡力学行为的3个主要影响因素。岩桥越接近坡顶,改进运动单元法所得安全系数越大,而Jennings法无法反映岩桥位置的影响效应。高贯通度的结构面导致岩质边坡发生“结构面滑移-岩桥剪断”复合型破坏模式,安全系数较小;而低贯通度的结构面导致完整岩石发生破坏,安全系数较大。水平或陡倾角结构面导致滑裂面穿切结构面,安全系数较大;而对于其它倾角情况下的结构面,岩质边坡发生“结构面滑移-岩桥剪断”复合型破坏模式,安全系数较小。实例应用结果说明该方法可以有效评价岩质边坡的稳定状态,可在类似工程中应用推广。

Previous studies on the kinematical element method have mainly focused on analyzing the stability of soil slopes,whereas little attention has been paid to the rock slope stability problem.Rock mass usually contains various discontinuities of different characteristics that play a dominant role in the mechanics behavior of rock slope.However,conventional methods are not applicable to analyze the combination failure on the rock bridge and the discontinuities.To solve the problem of rock slope stability controlled by discontinuities,vertex kinematic constraint conditions of the plastic sliding zone in the rock bridge and on the discontinuity were investigated.Kinematical element formulations were derived to calculate the factor of safety of the rock slope containing discontinuities.The improved kinematical element method was presented.Classic examples were given for demonstrating the validity of the results obtained by the improved kinematical element method.The results show that the location of rock bridge,the discontinuity persistence and the discontinuity inclination are found to have the dominant effects on the mechanics behavior of the rock slope.The factor of safety with the rock bridge near the slope toe is larger,whereas the Jennings method provides no information on the influence of the location of rock bridge.A high discontinuity persistence causes a rock slope to fail in the combined failure mode with a lower factor of safety,whereas a low discontinuity persistence leads to the failure of intact rock with a higher factor of safety.A horizontal or sub-vertical/vertical discontinuity leads a slope to fail in a mode of cutting through the discontinuity with a higher factor of safety,whereas other discontinuity inclinations cause the combined failure with a lower factor of safety.The proposed method can effectively evaluate the stability state of rock slope,and can be applied in similar practical engineering.